Smoke,heat and excessive moisture multiple alarm device



R. H. VOIGT Sept. 23, 1969 SMOKE; HEAT AND EXCESSIVE MOISTURE MULTIPLE ALARM DEVICE Filed'April 26, 1966 2 Sheets-Sheet 1 FIGZ INVENTOR ROBERT a vow-r BY M, Aw,

'ATTORNEYS Sept. 23, 1969" VQIGT 3,469,250

SMOKE, HEAT AND EXCESSIVE MOISTURE MULTIPLE ALARM DEVICE Filed April 26, 1966 2 Sheets-Sheet p,

MENTOR Roaur H. VOI6T A w, 1 V r ATTORNEYS United States Patent 3,469,250 SMOKE, HEAT AND EXCESSIVE MOISTURE MULTIPLE ALARM DEVICE Robert H. Voigt, Milford, Mich., assignor to Dynatron Incorporated, Milford, Mich., a corporation of Michigan Filed Apr. 26, 1966, Ser. No. 545,369 Int. Cl. G08b 21/00 US. Cl. 340237 12 Claims ABSTRACT OF THE DISCLOSURE A multiple alarm device for giving an alarm for ambient smoke condition accompanied or not by an elevated temperature and a rapid rate of rise of ambient temperature, and also capable of detecting excessive The present invention relates to alarms and parti cularly to an electronic control device capable of produclng an audible alarm in the presence of smoke, fire, or excessive moisture. More particularly, the present invention relates to a multiple alarm device incorporating a solid state component for its major control function and a novel combination smoke and excessive moisture detector for its major input function.

Up to the present, most alarm devices using a smoke detector as an input have employed gaseous thyratron tubes that in time become unstable and which have a limited life expectancy. In addition, most prior art fire and smoke alarm devices require constant voltage transformers that are bulky, thereby adding greatly to the cost of the device and to the space requirements therefor.

The present invention provides a fire, smoke and excessive moisture detecting device which is operable to sound an audible alarm upon activation in the presence of smoke, fire, excessive heat, or excessive moisture within the vicinity of the apparatus. The use of a single solid state component greatly increases reliability and substantially decreases space requirements and costs in manufacturing the device.

An ambient smoke condition accompanied or not by an elevated temperature and a rapid rate of rise of ambient temperature generally results from a fire, and an excessive moisture in the atmosphere may result from a defective steam radiator or an excessive steam pressure in a steam heating system, or yet, a defective hot water radiator or heater. An excessive moisture may also result, in hospital rooms or in nurseries, from a vaporizer being turned up too high. In addition, under some circumstances, a fire condition may drive excessive moisture into areas above the fire.

It is consequently a principal object of the invention to provide a multiple alarm device capable of producing an audible alarm in the presence of smoke, fire or excessive moisture.

It is another object of the present invention to provide a multiple alarm device of substantially small size and utilizing a single solid state component for the major control function of the device.

It is a further object of the present invention to provide a multiple alarm device having a maximum reliability as a result of utilizing a single solid state component for senslng temperature, for sensing the rapid rise in ambient temperature, and for controlling the alarm producing means the presence of smoke, elevated temperature, or excessive molsture.

It is yet another object of the invention to provide a multiple alarm device which is low in manufacturing cost, which is simple to adjust, and which is endowed with a long life and with reduced maintenance.

Other objects and advantages of the present invention will readily occur to those skilled in the art to which the invention pertains upon reference to the following description considered in conjunction with the attached drawings, wherein like reference characters refer to like parts and in which:

FIG. 1 is a perspective view of an example of a multiple alarm device according to the principle of the invention;

FIlrIG. 2 is a schematic circuit diagram of the device of FIG. 3 is an elevational view of the device of FIG. 1, with some portions broken away to show some of the internal construction, and with the combination smoke and excessive moisture detector portion thereof shown in section;

FIG. 4 is an enlarged partial section along line 44 of FIG. 3;

FIG. 5 is a partial section similar to FIG. 3, showing the smoke detection function of the combination smoke and excessive moisture detector; and

FIG. 6 is a figure similar to FIG. 5, but showing the excessive moisture detection function of the combination smoke and excessive moisture detector of the invention.

Referring now to the drawings, and more particularly to FIG. 1 and FIG. 3 thereof, an example of a practical embodiment of a multiple alarm device according to the invention comprises a housing 10, made of thin metal such as sheet steel, aluminum, or the like, closed at one end, as shown at 12, and having an opening normally obturated by a base member 14, made of molded material such as rubber or the like. On the end of the base member 14 opposite the end engaged within the open end of the housing 10 is mounted a combination smoke and moisture detector, designated generally at 16 and which, as best seen in FIG. 3, comprises a plurality of louvreforming annular elements or light baffle rings 18, V- shaped when seen in cross-section, and normally piled on top of one another with spacer segments, such as shown at 20, FIG. 4, interposed between consecutive annular light baffle rings. The baffle rings 18 are surmounted by av cover plate 22 having an annular peripheral V-shaped portion 24, so as to conform to the shape of the baffle rings 18 and spacer segments 20, the generally discshaped cover plate 22 being in turn surmounted by a disc-shaped flat name-plate 26. As best seen in FIG. 3 and FIG. 4, the assembly formed by the superposed bafiie rings 18, with a pair of spacer members 20, diametrically disposed, placed between two consecutive bafile rings, is held in assembly and mounted or affixed to the base 14 by means such as elongated screws 28 passing through alined holes in the baffle rings and the spacer members, and having a threaded end passing through adequate bores, not shown, in the base, the whole assembly being held together by means such as screws and ordinary washer or nuts, not shown. The upper face, as seen in FIG. 3 of the base 14, is provided with a projecting peripheral V-shaped annular portion 30, so as to form an adequate base for the light bafile assembly 17, which thus defines a cavity, or enclosure 32, impermeable to ambient light, but permeable to ambient atmosphere. The

surface of each light baflle ring 18 and spacer member 20 is coated with a thin coating of black dull copper oxide, and the surface 34 of cover plate 22 forming the end face of cavity 32 is also blackened by a thin coating of copper oxide providing a substantially mat and non-reflective surface finish. Within the bottom surface of cavity 32, formed by the top face of base 14, are imbedded a neon lamp 36 and a photoconductor cell 38, placed in substantial close proximity, with the neon lamp 36, however, disposed deep enough so that the direct light emitted thereby is prevented from impinging upon the active ele ment of the photoconductor cell 38.

As shown in FIG. 1, the illustrated example of the multiple alarm device according to the invention, is pro{ vided with an input plug 40 having prongs 42 and 43- for insertion into an ordinary AC wall receptacle, not shown,- and to which are connected power lines supplying electric power to the device through double conductor electric cable 44. In addition, housing is provided with a bracket 46 for attachment of the alarm device in any convenient location, and manual adjusting means, as; shown at 48, are also provided for the purpose of adjust ing the sensitivity of the device as hereinafter explained. The alarm producing portion of the apparatus comprises an electromagnetic clapper housed in a box mounted on the closed end of the housing 10, as shown at 50 in FIG. 3, and held therein by means of any conventional means such as screws 52. The circuit portion of the apparatus is mounted upon a disc-like printed circuit or board 54 attached below the base 14 as seen in the drawing, and held in position in a conventional manner by being provided with holes, not shown, through which pass the threaded ends of screws 28 engaged by nuts not shown, disposed below the board 54. The circuit board 54 thus forms a unitary assembly with base 14 and smoke and moisture detector 16, the periphery of the rubber-like base 14 being frictionally engaged into the open end of the housing 10. As seen in FIGS. 1 and 3, a silicon controlled rectifier 56 is mounted on the outside of the base 14, for the purpose to be hereinafter explained in detail.

Referring now to the circuit diagram of FIG. 2, prongs 42 and 43 of plug 40 are connected respectively to power lines 58 and 59. An AC voltage regulating circuit, or clipper regulator circuit, comprising dropping resistor 60 and double anode Zener diode 61, is connected across the AC power lines 58 and 59. Electromagnetic alarm giving element 50 comprises a coil 62 and a clapper 63, coil 62 being connected between power lines 58 and 59 in series with the silicon controlled rectifier 56, the anode 64 of the silicon controlled rectifier being connected to power line 59. A transient filter capacitor 68 is shunt connected across the anode 65 and cathode 66 of the silicon controlled rectifier 56.

The gate 69 of silicon controlled rectifier 56 is connected to a control circuit comprising a rectifying diode 70 in series with a potentiometer 71, the anode of the rectifying diode 70 being connected at the junction between dropping resistor 60 and double anode Zener diode 61. Potentiometer 71 has an adjustable tap or slider 72 which is connected to the gate 69 of the silicon controlled rectifier 56 through photoconductor cell 38. A temperature compensating thermistor, having a negative temperature coefficient and shown at 73, is shunt connected between the gate 69 and the cathode 66 of the silicon controlled rectifier56.

A regulated light source is provided by disposing the neon lamp 36 in series with its current limiting resistor 74 across the common junction formed by the output terminal of dropping resistor 60 and one of the anode of double anode Zener clipping diode 61 and power line 59. In this manner, neon lamp 36 forms a light source, the light intensity of which is regulated by double anode Zener clipping diode 61 providing a substantially constant voltage across the neon lamp.

The operation of a multiple alarm device according to the herein example of the invention is as follows:

Referring to FIG. 3, the light emitted by neon lamp 36, being prevented from directly striking photoconductor cell 38, is emitted within the dark cavity or enclosure 32 in the direction of surface 34 of end plate 22. As the surface 34 andthe annular baflle rings 18 are coated with a non-reflecting black copper oxide, practically no light is reflected back from surface 34, in view of the high light absorbing quality of the surface, and photoconductor cell 38 remains undisturbed. It is apparent that no light can penetrate into cavity 32 from the ambient, as the assembly of bafile rings 18 acts as a perfect light screen in view of the angle of their V-shaped annular portion, thus preventing direct light from penetrating into the cavity.

As no or very little light strikes photoconductor cell 38, the resistance of the photoconductor cell remains relatively high and current flow through the gate 69- cathode 66 circuit of silicon controlled rectifier 65 is below the current flow causing firing of the silicon controlled rectifier. Consequently, the anode 65-cathode 66 circuit of the silicon controlled rectifier remains in a nonconducting state. The silicon controlled rectifier 56 is disposed externally to the housing 10 and is thus caused to rapidly respond to changes in ambient temperature due to the small mass of the silicon controlled rectifier.

As the spaced-apart baffle rings 18 permit ambient air to circulate freely through cavity 32, in the presence of smoke, smoke enters the cavity 32 and light emitted from neon lamp 36 is reflected by the smoke particles and is caused to strike the photoconductor cell 38, see FIG. 5, thus substantially decreasing the resistance of the photoconductor cell and increasing the current flow through the gate 69-cathode 66 circuit of the silicon controlled rectifier 56, thus causing a pulsating direct current to flow from power line 59 through the cathode 66-anode 65 circuit of the silicon controlled rectifier and back to power line 58 through the coil 62 of the electromagnetic clapper 50, thus causing clapper 63 to strike the housing, resulting in an audible alarm.

Under smoke and fire conditions, the silicon controlled rectifier 56, being located externally to the housing 10 and having a small mass, responds rapidly to temperature rise associated with fire conditions. Since a silicon controlled rectifier fires at a lower gate current at high temperature than it does at low temperature, under smoke and fire conditions, silicon controlled rectifier 56 becomes even more sensitive to the presence of smoke in cavity 32. As shown in FIG. 3, temperature compensating thermistor 73 being located internally of the housing 10, temperature compensating thermistor 73 is not in direct contact contact with the ambient and does not immediately respond to an increase in ambient temperature. Therefore, the increase in shunting elfect due to the presence of temperature compensating thermistor 73 between the gate 69 and the cathode 66 of the silicon controlled rectifier 56 which would normally render the silicon controlled rectifier less sensitive, does not take place. Consequently, as soon as the temperature of the silicon controlled rectifier 56 reaches a predeteriinined temperature, the silicon controlled rectifier selfres.

As tap or slider 72 of potentiometer 71 is made adjustable by being accessible through an access hole through the wall of housing 10, and is provided with the adjusting means identified at 48 in FIG. 1, such an adjustment of the position of tap 72 determines the initial gate current flow through the silicon controlled rectifier 56 and is generally normally set to a threshold firing current at a temperature of 75 degrees F. Under such a setting, the silicon controlled rectifier 56 will self-fire at an ambient temperature of about degrees F. to degrees F. to produce an audible alarm.

If the ambient temperature rise is very rapid, as will be the case under a fire condition, the self-firing temperature point of the silicon controlled rectifier 56 will be less than the 135 to 145 degree F. range of normal firing. For example, if the normal ambient temperature setting by means of tap 72 of potentiometer 71 corresponds to a temperature of 75 degrees F, and a fire raises the ambient temperature to 110 degrees F. within a period of four minutes or less, thus resulting in a rise of 35 degrees F. in four minutes or less, an alarm sounds as the temperature compensating thermistor 73, being located inside the control housing 10, remains at substantially the original ambient temperature of 75 degrees F. and the shunting effect of the thermistor 73 is substantially less than it would be if the thermistor was also at 110 degrees F.

Under conditions of very slow rise in ambient temperature, the temperature of thermistor 73 follows the ambient temperature rise and as the thermistor temperature remains substantially the same as the temperature of the silicon controlled rectifier 56, thermistor 73 does not shunt out the increased sensitivity of the silicon controlled rectifier and the alarm does not sound at 110 degrees F. as would happen in the case of rapid rate of temperature rise. The temperature versus resistance curve of thermistor 73 is such that at some point the silicon controlled rectifier will self-fire regardless of the temperature of the thermistor. Under conditons of slow temperature rise, the alarm sounds on the high activation temperature side, somewhat in the neighborhood of 145 degrees F. Consequently, it can be seen that the combination of rapid rate of temperature rise or above normal rate of rise resulting from the fire together 'with a smoke condition causes the device to be very sensitive. A very rapid rise in ambient temperature, unaccompanied by smoke, results in slight reduction of the sensitivity of the device. A slow ambient temperature rise, by causing thermistor 73 to substantially follow the rise in temperature of the silicon controlled rectifier 56, renders the device still less sensitive.

Under conditions of excessive moisture, which as previously mentioned may result from a defective heating system or from a vaporizer operating at too high an output in a babys room or patients room, or yet which could result from a fire condition at a level lower than the level on which the alarm device of the invention is located, the moisture laden air circulating through cavity 32 causes condensation on surface 34 of end plate 22. The condensation on surface 34 is caused by the temperature of end plate 22 being slightly less than the temperature of the ambient because plate 22 is partially insulated from the ambient by the air space situated between end plate 22 and name plate 26. Condensation on surface 34 of end plate 22 causes the surface to become more light reflecting as the dull black surface finish caused by the copper oxide becomes relatively wet and glistening, consequently more light reflective than when un'wet. The condensation effect on surface 34 is greatly favored by the hygroscopic quality of the black copper oxide coating the surface. As surface 34 of end plate 22 becomes more light reflective, see FIG. 6, the light rays emitted by neon lamp 36 are consequently reflected by surface 34 and impinge upon photoconducting cell to the point of passing sufficient current to gate 69 of silicon controlled rectifier 56, see FIG. 2, to fire the silicon controlled rectifier to cause an audible alarm. As soon as the unit dries, surface 34 of end plate 22 returns to its usual lull, nonreflective state and the device returns to normal.

Under any condition of alarm, if the duration of activation exceeds about 5 seconds, the alarm automatically locks in due to the self-heating of the silicon controlled rectifier 56 caused by the passage of a substantially high current therethrough. Such a locking condition of an alarm according to the invention is a very advantageous feature since, under certain fire conditions, a draft of fresh substantially cool air could fan the unit and momentarily drive its temperature below the firing temperature, or blow the smoke out from the cavity 32 for a short period of time. Such draft of cool fresh air could be caused by a window or door being blown open, or simply by normal flow of fresh air to replace the atmospheric oxygen being consumed by the fire. The self-locking feature of the invention prevents the unit from being turned off under those conditions, and as soon as the alarm is turned on, it remains on until the condition causing the alarm has been rectified.

With the passage of time, the light output of neon lamp 36 tapers off, due to ionization blackening of the glass envelope, thus causing the unit to become potentially less sensitive due to the act that less light impinges upon the photoconductor cell 38 under a smoke or a moisture condition. Consequently, the silicon controlled rectifier 56 is potentially less sensitive, and periodic threshold adjustments are necessary. Generally, biyearly adjustments of tap 72 of potentiometer 71 are required by way of adjusting means 48. An incandescent lamp could be used instead of the preferable neon lamp 36, but the normal life of an incandescent lamp is generally less than five years and filament rupture is always potentially possible due to vibrations or current surges. A neon lamp, on the contrary, has a life expectancy of at least ten years and will generally last for at least twentyfive years. In addition, a neon gaseous lamp requires 2 milliamperes or less of current flow, thus reducing the cost of operating a multiple alarm device according to the invention to less than a few pennies per month.

What is claimed as new is:

1. An alarm system adapted for connection to a source of electrical power comprising:

(a) an alarm circuit connected across said source of electrical power and having solid state switching means and means for producing an audible alarm upon activation of said solid state switching means;

(b) said solid state switching means being exposed to ambient temperature and capable of self-activation upon being heated to a predetermined temperature;

(c) means providing adjustable voltage bias for controlling the threshod of self-activation of said solid state switching means at said predetermined temperature;

(d) temperature responsive means insulated from said ambient temperature; and

(e) means controlled by said temperature responsive means and ada ted to modify said voltage bias as a function of the temperature of said temperature responsive means.

2. The system of claim 1 further comprising:

(a) light emitting means adapted to supply a substantially constant light output;

(b) light responsive means disposed adjacent to said light emitting means; and

(c) means adapted to modify said voltage bias in function of the amount of light impinging upon the light responsive means.

3. The system of claim 1 wherein said solid state switching means is a silicon controlled rectifier.

4. The system of claim 2 wherein:

(a) said light emitting means and said light responsive means are placed within a cavity impermeable to ambient light and permeable to ambient atmosphere;

and

(b) means are provided for shielding said light responsive means from direct light from said light emitting means while allowing reflected light to impinge upon said light responsive means.

5. The system of claim 4 wherein:

(a) the inside surfaces of said cavity are normally nonreflective; and

(b) said surfaces are adapted to become light reflective upon exposure to a predetermined level of ambient moisture.

6. The system of claim 5 wherein said surfaces are coated with a hygroscopic normally dull finish of black copper oxide.

7. An alarm system for connection to a source of electrical power comprising:

(a) an alarm circuit connected across said source of electrical power comprising in series:

(1) means for producing an audible alarm upon passage of electrical current therethrough; and

(2) normally open solid state switching means capable of closing upon being heated to a predetermined temperature;

(b) adjustable means adapted to provide an adjustable voltage bias for causing said solid state switching means to close upon being heated at said predetermined temperature; and

(c) means adapted to modify said voltage bias in response to control signals for causing said solid state switching means to close at a temperature diflerent from said predetermined temperature, said last mentioned means comprising:

(1) temperature responsive resistive means substantially thermally insulated from the ambient;

(2) said solid state switching means being therr'nally exposed to the ambient; and

(3) said temperature responsive resistive means being disposed so as to shunt said adjustable voltage bias for causing said solid state switching means to close upon a lower ambient temperature when said temperature responsive resistive means is relatively cold and at a higher temperature when said temperature responsive resistive means is relatively hot.

8. The system of claim 7 wherein said means adapted to modify said voltage bias comprises:

(a) light emitting means adapted to supply a substantially constant light output;

(b) light responsive means shielded from direct exposure to said light emitting means and adapted to supply a signal output in response to exposure to reflected light;

(c) an enclosure impermeable to ambient light and permeable to ambient atmosphere;

(d) inner surfaces in said enclosure adapted to be normally non-reflective to light; and

(e) whereby the presence of smoke within said enclosure causes light emitted by said light emitting means to impinge upon said light responsive means for causing a signal output therefrom to modify said voltage bias.

9. The system of claim 8 wherein said inner surfaces are coated with a normally dull non-reflective coating adapted to become light reflective upon contact with moisture laden ambient atmosphere.

10. The system of claim 9 wherein said coating consists of hygroscopic black copper oxide.

11. The system of claim 7 wherein said solid state switching means is a silicon controlled rectifier.

12. The system of claim 7 wherein said adjustable means adapted to provide an adjustable bias comprises:

(a) a double anode Zener diode connected across said source of electrical power.

(b) a rectifier diode and a voltage divider connected in parallel with said double anode Zener diode; and

(0) adjustable tap means on said voltage divider electrically connected to the input of said solid state switching means.

References Cited UNITED STATES PATENTS 1,883,116 10/1932 Tomlinson 250218 XR 2,604,597 7/1952 Cahusac et al. 3,280,392 10/ 1966 Benda 3l7--235 3,284,787 11/1966 Voigt et al. 340227 3,383,670 5/ 1968 Roberts.

JOHN W. CALDWELL, Primary Examiner DANIEL K. MYER, Assistant Examiner US. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,469 ,250 September 23 1969 Robert H. Voigt peers in the above identified It is certified that error ap e hereby corrected as patent and that said Letters Patent ar shown belowlr:

Column 4, line 40, "clapper" should read element Column 5, line 65, "lull" should read dull Signed and sealed this 3rd day of February 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, 1B

Edward M. Fletcher, J r.

Commissioner of Patents Attesting Officer 

